The present invention relates to biopsy instruments used in collecting specimens of tissue from the skin or internal organs for analysis. The invention particularly relates to skin punch biopsy devices which are conventionally used to bore cylindrical channels in the skin by rotating a tubular cutting sleeve to advance the sleeve into tissue.
A serious problem which has occurred with conventional punch type biopsy instruments is that these instruments are incapable of separating the tissue specimen from the surrounding tissue once the rotational cutting action has been completed. Almost invariably, as the biopsy instrument has been withdrawn, the tissue specimen remains attached to the body at the uncut portion of its base and must then be lifted with a needle point or tweezers and the attached base portion excised with a scalpel blade. This secondary operation is not only tedious and time consuming but also requires additional equipment in the form of a scalpel and unnecessarily places medical personnel at risk for such infectious diseases as hepatitis and AIDS through accidental needle punctures, scalpel cuts, or blood splashes. Also, this secondary removal operation is very difficult to perform on agitated human patients or on unwieldy animals.
An additional problem which arises with conventional skin punch biopsy instruments concerns the fact that the collected biopsy specimens are normally placed in a vial containing preservative solution. Thus, specimens which are small in size are often difficult to find and retrieve, especially if the preservative solution has been darkened with blood or other body fluids from the specimen.
One attempt to solve some of the above-mentioned problems is found in U.S. Pat. No. 4,785,826, issued to Ward. This patent discloses a biopsy needle having a first hollow member with a second elongated hollow member fitted within the first hollow member. The second member has a flexible end portion included pointed segments which are normally opened to receive a tissue specimen, and which can be closed by moving the inner member axially with respect to the outer member (by means of twisting one with respect to the other). The tapered segments are deformed by a shoulder formed on the inner surface of the outer member, thereby being bent inwardly to cut and capture a tissue specimen.